In related technologies, in order to meet a high-efficiency requirement, the concept of multi-carrier is introduced in a system.
A base station can be configured with multiple carriers which may be classified into fully-configured carriers and partially-configured carriers, wherein a fully-configured carrier includes all necessary synchronous channels, control channels and other system side information, while a partially-configured carrier may only include data transport channels or some necessary control messages; compared with a fully-configured carrier, a partially-configured carrier may not include synchronous channels.
Carriers may be classified into main carriers and sub-carriers at a terminal side.
A main carrier, which must be a fully-configured carrier, is mainly used for control message interaction and/or data interaction between a base station and a terminal, and may be further used for service processing and physical (PHY for short) control information or media access control (MAC for short) information interaction; additionally, a main carrier may be further used for completing part terminal control functions such as network access. It should be noted that each terminal has only one main carrier in a cell.
A sub-carrier, which may be a fully-configured carrier or a partially-configured carrier, is an additional carrier for the service transmission of a terminal and is mainly used for data interaction. A sub-carrier may also include a control signaling supportive of multi-carrier operation. A terminal may have one or more sub-carriers or no sub-carrier.
In a mobile communication system, when a terminal moves to the edge of a base station, if the original serving base station is reduced in the signaling quality and thus incapable of continuing to provide services for the terminal, the terminal should be handed over to another base station to maintain the succession of the services, wherein such a handover is known as an inter-base station handover.
In a multi-carrier system, as a base station is provided with multiple carriers, when a carrier (serving carrier) being used by a terminal is over-loaded and thus the quality of service (QoS) is reduced, or when the signal intensity of a serving carrier is reduced and thus the terminal needs to search for a carrier of a better intensity, the terminal may be handed over to another carrier in the base station to perform data transmission, wherein such a handover is known as intra-base station handover.
In a single-carrier system, a base station broadcasts information of a neighbor cell (a cell neighboring to the current serving cell) via broadcast information to support a terminal to scan the neighbor cell, so that the terminal can measure the signal quality of the neighbor cell, wherein in the broadcast information, there is a base station identifier of the neighbor cell and other information. In a multi-carrier system, a base station may be configured with multiple carriers and can broadcast the multi-carrier information of the serving base station via broadcast information. When a serving carrier cannot provide good radio quality for a terminal, the terminal will send a scan request to the base station to request a scan on the carriers of the current serving base station or the carriers of a neighbor multi-carrier base station, however, currently there is no corresponding solution that a base station sends a scan response to a terminal. In addition, in the current technologies, when a terminal needs handover and the handover is triggered by a serving base station, there is no corresponding solution that the handover request signaling sent from the serving base station to the terminal includes the carriers the terminal needs to scan.